Guided discovery of hepatoprotective polyhydroxy cembrane-type diterpenoids from the gum resin of Boswellia carterii by MS/MS molecular networking.

Seven previously undescribed polyhydroxy cembrane-type diterpenoids, olibanols A-G (1-7) were obtained from the gum resin of Boswellia carterii by means of MS/MS molecular networking. Compound 2 possessed four hydroxy groups, 1, 3, 4, 5, and 6 had three hydroxy groups, 7 with one hydroxy group, among which 1 and 4 were a pair of epimers with double bond at C-3 and hydroxy at C-8. Structures of these previously undescribed compounds were determined by NMR analysis and ECD calculations. All the polyhydroxy cembrane-type diterpenoids obtained were assayed for their hepatoprotective effects against the anti-tuberculosis drug-induced hepatic damage to the HRZ-induced HepG2 cells. As results indicated, compounds 3, 4, and 6 showed significant hepatoprotective effects against the hepatic damage via the Nrf2 signal pathway, which could be developed as potential hepatoprotective agents against the anti-tuberculosis drug-induced hepatic damage.